Enji Fujita

Co/Pd multilayer media with Pd inorganic granular seed layer for perpendicular recording

We have investigated the Co/Pd multilayer media with a Pd–SiN granular seed layer as perpendicular recording media. The Pd–SiN granular seed layer and the Co(0.2 nm)/Pd(0.8 nm) multilayer were formed by dc and rf sputtering at room temperature on a FeTaC soft magnetic underlayer. The Pd–SiN granular seed layer of 3 nm was very effective to get good magnetic properties with coercivity of 3.9 kOe, a nucleation field of −2.1 kOe, and a M–H slope parameter 4π(dM/dH)H=Hc of 1.4. In addition, it was found that growth of multilayer grains is sensitive to surface conditions of the soft magnetic underlayer. The average column diameter of 13.7 nm with a dispersion of 21.7% was evaluated from the plan-view transmission electron microscope image of well-separated Co/Pd columns with a boundary, which was grown on the Pd–SiN seed layer and the soft magnetic underlayer with Ar plasma etching. Atomic force microscope measurements showed that mean roughness (Ra) of the FeTaC surface decreased from 0.46 to 0.39 nm by the p...

Perpendicular magnetic recording media based on Co-Pd multilayer with granular seed layer

We have investigated Co-Pd multilayers deposited on a Pd-SiN granular seed layer and a FeTaC soft magnetic underlayer (SUL) for perpendicular magnetic recording. The Pd-SiN granular seed layer of 3 nm was found to be very effective for good magnetic properties with coercivity of 3.9 kOe, a negative nucleation field of -2.1 kOe, and a M-H loop slope parameter 4/spl pi/ (dM/dH)/sub H=Hc/ of 1.3. The average column diameter of 13.7 nm with a dispersion of 21.7% was evaluated from the transmission electron microscopy image of well-separated columns with a clear boundary. This Co-Pd medium gave better playback performances by a merged ring giant magnetoresistive head compared to the medium with a Pd seed layer. The effect of Ar plasma etching on the SUL was also investigated to improve playback performance.

Enhancement of exchange coupling for antiferromagnetically coupled media

Antiferromagnetically coupled (AFC) media with CoPt or Co interlayers inserted between a Ru layer and CoCrPtB magnetic layers were prepared in order to enhance the exchange coupling and the thermal stability. The exchange coupling field Hex increased from 0.6 to 4.2 kOe by increasing the thickness of the Co interlayer from 0 to 1 nm. The coupling energy J increases with increasing thickness of the interlayer. The coupling energy J of the AFC media with the interlayer are ten times larger (for 1-nm-thick Co interlayer) and five times larger (for 1-nm-thick CoPt interlayer) than that of the medium without the interlayer. Thermal stability factor KuV/kBT for the media with 1-nm-thick Co and 1-nm-thick CoPt interlayers are about 10% larger than that for the medium without the interlayer. The results suggest that the enhancement of the exchange coupling energy induces the increasing of KuV/kBT in the AFC media.

Cross-sectional control of boron contents and the microstructures of Co/Pd multilayer perpendicular magnetic recording media

The effects of cross-sectional modulated boron segregation on Co/PdB multilayer perpendicular magnetic recording media have been studied. Gradually reduced boron contents from thin PdB seed layer (33 at.%) to the top of the Co(0.2 nm)/PdB (0.8-nm) multilayer (12.5 at.% at the center of the multilayer) were successively achieved and confirmed by the depth-profile of X-ray photoelectron spectroscopy (XPS). Observed magnetic properties and magnetic force microscopy images suggested that this gradient diffusion supports reduction of intergrain exchange coupling and improvement of the magnetic properties. The signal-to-noise ratio over 22 dB was obtained at 450 kFCI in playback tests, in combination with amorphous cobalt boron soft-magnetic underlayer (SUL). It is suggested that these properties are brought by a combination of the dispersed nucleation sites with rich boron content in the initial layer and decreasing boron content during the growth of the multilayer. In addition, this simple medium, which consists of only three elements, Co, Pd, B, for the SUL, the seed layer, and the magnetic layer, has a very unique feature of the dull interfaces, observed by a transmission electron microscope.

In-Plane Crystalline Orientation and Magnetic Anisotropy of Co-Ni-Zr Media

The in-plane crystalline orientation of a longitudinal thin film medium was investigated to clarify the relation between the crystalline orientation and the magnetic anisotropy. As is well known, the anisotropy is induced by deposition onto a moving disk substrate (transport deposition) and is changed by substrate texturing. It has heretofore been difficult to determine the crystalline orientation by X-ray diffraction because of the very intense background reflection. We have developed a precise background correction method enabling measurement of the pole figure of the longitudinal medium. It is clear that the c-axis of a medium on a mirror-polished substrate is essentially oriented in the direction of substrate motion, and that the axis of a medium on a textured substrate tends to be oriented in the texturing direction.

Microstructure and segregation effect of Co/Pd multilayer perpendicular magnetic recording media

In this report, we have investigated addition of boron with modulated contents in depth profile and microstructure by a transmission electron microscopy (TEM) with high annular angle dark field (HAADF) detector to evaluate segregation effect.